U.S. patent application number 11/948697 was filed with the patent office on 2008-03-27 for stepping motor control apparatus, stepping motor control method and stepping motor control program product.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Yasuhiko YOSHIHISA.
Application Number | 20080074072 11/948697 |
Document ID | / |
Family ID | 37052474 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080074072 |
Kind Code |
A1 |
YOSHIHISA; Yasuhiko |
March 27, 2008 |
STEPPING MOTOR CONTROL APPARATUS, STEPPING MOTOR CONTROL METHOD AND
STEPPING MOTOR CONTROL PROGRAM PRODUCT
Abstract
There are included a control circuit to control sequence of
excitation of a stepping motor, a switching circuit to switch
electric power to be supplied to the stepping motor based on an
instruction from the control circuit, and a stop circuit to stop an
operation of the switching circuit in a case where temperature of
the switching circuit becomes a specified temperature or higher,
and the control circuit controls the switching circuit in a mode
where the stop circuit operates before the stepping motor is
damaged by heat.
Inventors: |
YOSHIHISA; Yasuhiko;
(Nagano, JP) |
Correspondence
Address: |
SUGHRUE, MION, PLLC
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3213
US
|
Assignee: |
SEIKO EPSON CORPORATION
|
Family ID: |
37052474 |
Appl. No.: |
11/948697 |
Filed: |
November 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11368526 |
Mar 7, 2006 |
7327115 |
|
|
11948697 |
Nov 30, 2007 |
|
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Current U.S.
Class: |
318/696 |
Current CPC
Class: |
Y10S 388/934 20130101;
H02P 8/36 20130101 |
Class at
Publication: |
318/696 |
International
Class: |
H02P 8/36 20060101
H02P008/36 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 7, 2005 |
JP |
P2005-062026 |
Claims
1. A printing apparatus comprising: a recording head for printing a
medium; a stepping motor provided in the printing apparatus; a
control circuit that controls sequence of excitation of the
stepping motor; a switching circuit that switches electric power to
be supplied to the stepping motor based on an instruction from the
control circuit; and a stop circuit that stops an operation of the
switching circuit when temperature of the switching circuit becomes
a specified temperature or higher, wherein the control circuit
controls the switching circuit such that the stop circuit operates
before the stepping motor is damaged by heat.
2. The printing apparatus according to claim 1, wherein the control
circuit adjusts an off time in which a switch constituting the
switching circuit keeps an off state, and thereby the control
circuit controls the switching circuit.
3. The printing apparatus according to claim 2, wherein the control
circuit adjusts the off time in accordance with a set value of
current to be outputted to the stepping motor.
4. The printing apparatus according to claim 2, wherein the control
circuit adjusts the off time in accordance with a kind of decay of
the switching circuit.
5. A printing apparatus comprising: a recording head for printing a
medium; a stepping motor provided in the printing apparatus; a
control circuit that controls sequence of excitation of the
stepping motor; a switching circuit that switches electric power to
be supplied to the stepping motor based on an instruction from the
control circuit; and a stop circuit that stops an operation of the
switching circuit when temperature of the switching circuit becomes
a specified temperature or higher, wherein the control circuit
controls an off time in which a switch constituting the switching
circuit keeps an off state between a first time in which the
stepping motor is not damaged by heat at a specified duty and a
second time in which the stop circuit operates at the specified
duty.
6. The printing apparatus according to claim 5, wherein the
specified duty is 100%.
7. A printing apparatus comprising: a recording head for printing a
medium; a stepping motor provided in the printing apparatus; a
control circuit that controls sequence of excitation of the
stepping motor; and a switching circuit that switches electric
power to be supplied to the stepping motor based on an instruction
from the control circuit, wherein the control circuit, when the
switching circuit becomes a predetermined temperature or higher,
prolongs an off time in which a switch constituting the switching
circuit keeps an off state.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of application Ser. No. 11/368,526
filed Mar. 7, 2006. Priority is claimed from JP 2005-062026 filed
Mar. 7, 2005. The entire disclosures of the prior application,
application Ser. No. 11/368,526, and the above-identified priority
document, are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field of the Invention
[0003] The present invention relates to a stepping motor control
apparatus, a stepping motor control method and a stepping motor
control program product.
[0004] 2. Description of the Related Art
[0005] A conventional stepping motor control apparatus generally
adopts such a method that reference is made to a table indicating a
relation between the position of a rotator of a stepping motor and
the phase of excitation, the excitation current corresponding to
the position of the rotator is made to flow, and the rotator is
rotated to a desired angle (see JP-A-2002-281788 (Abstract,
Claims)).
[0006] In the conventional stepping motor control apparatus, in the
case where for example, a program for control runs away, since
current continues to be supplied to the stepping motor, there is a
problem that the stepping motor is heated and is burnt out in some
cases.
SUMMARY OF THE INVENTION
[0007] The invention has been made in view of the above
circumstances, and has an object to provide a stepping motor
control apparatus, a stepping motor control method, and a stepping
motor control program product, in which even in the case where a
program or the like runs away, it is possible to prevent a stepping
motor from being burnt out.
[0008] In order to achieve the foregoing object, according to an
aspect of the invention, a stepping motor control apparatus
includes a control circuit to control sequence of excitation of a
stepping motor, a switching circuit to switch electric power to be
supplied to the stepping motor based on an instruction from the
control circuit, and a stop circuit to stop an operation of the
switching circuit in a case where temperature of the switching
circuit becomes a specified temperature or higher, and the control
circuit controls the switching circuit in a mode where the stop
circuit operates before the stepping motor is damaged by heat.
[0009] Accordingly, the stepping motor control apparatus can be
provided which can prevent the stepping motor from being burnt out
even in the case where a program or the like runs away.
[0010] Besides, according to a stepping motor control apparatus of
another aspect of the invention, in addition to the foregoing
invention, the control circuit adjusts an off time as a time in
which a switch constituting the switching circuit keeps an off
state and controls the switching circuit in the mode where the stop
circuit operates before the stepping motor is damaged by heat.
Thus, by adjusting the off time, it is possible to easily prevent
the stepping motor from being damaged by heat.
[0011] Besides, according to a stepping motor control apparatus of
another aspect of the invention, in addition to the foregoing
invention, the control circuit adjusts the off time in accordance
with a set value of current to be outputted to the stepping motor.
Thus, irrespective of the set current value, it is possible to
always stably prevent the stepping motor from being burnt out by
heat.
[0012] Besides, according to a stepping motor control apparatus of
another aspect of the invention, in addition to the foregoing
invention, the control circuit adjusts the off time according to a
kind of decay of the switching circuit. Thus, irrespective of the
kind of the decay, it is possible to certainly prevent the stepping
motor from being damaged by heat.
[0013] Besides, according to another aspect of the invention, a
stepping motor control method is a control method for a stepping
motor control apparatus including a control circuit to control
sequence of excitation of a stepping motor, a switching circuit to
switch electric power to be supplied to the stepping motor based on
an instruction from the control circuit, and a stop circuit to stop
an operation of the switching circuit in a case where temperature
of the switching circuit becomes a specified temperature or higher,
and the control circuit controls the switching circuit in a mode
where the stop circuit operates before the stepping motor is
damaged by heat.
[0014] Accordingly, the stepping motor control method can be
provided which can prevent the stepping motor from being burnt out
even in the case where a program or the like runs away.
[0015] Besides, according to another aspect of the invention, a
stepping motor control program is a control program for a stepping
motor control apparatus including a control circuit to control
sequence of excitation of a stepping motor, a switching circuit to
switch electric power to be supplied to the stepping motor based on
an instruction from the control circuit, and a stop circuit to stop
an operation of the switching circuit in a case where temperature
of the switching circuit becomes a specified temperature or higher,
and the switching circuit is controlled in a mode where the stop
circuit operates before the stepping motor is damaged by heat.
[0016] Accordingly, the stepping motor control program can be
provided which can prevent the stepping motor from being burnt out
even in the case where a program or the like runs away.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a view showing a structural example of a printing
apparatus of an embodiment of the invention;
[0018] FIG. 2 is a view showing a structural example of a tube pump
of the printing apparatus shown in FIG. 1;
[0019] FIG. 3 is a view showing a structural example of the tube
pump of the printing apparatus shown in FIG. 1;
[0020] FIG. 4 is a view showing a structural example of a control
system of the printing apparatus shown in FIG. 1;
[0021] FIG. 5 is a view showing a detailed structural example of a
motor control circuit shown in FIG. 4;
[0022] FIGS. 6A and 6B are views each showing a structural example
of a drive circuit shown in FIG. 5;
[0023] FIGS. 7A and 7B are views each showing an output current
waveform of the drive circuit shown in FIG. 6;
[0024] FIGS. 8A and 8B are views each explaining an off time and an
on time of the drive circuit shown in FIG. 6;
[0025] FIG. 9 is a view showing a relation among a current set
value, a decay and an off time;
[0026] FIG. 10 is a view showing a relation between a heat
generation amount and an off time;
[0027] FIG. 11 is a view showing a relation between a heat
generation amount and an off time;
[0028] FIG. 12 is a view showing a relation between a heat
generation amount and an off time; and
[0029] FIG. 13 is a view showing an output current waveform in a
mixed decay.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Hereinafter, an embodiment of the invention will be
described with reference to the drawings.
[0031] FIG. 1 is a view showing a structural example of a printing
apparatus using a stepping motor control apparatus of an embodiment
of the invention. Hereinafter, the embodiment of the invention will
be described with reference to FIGS. 1 to 9. FIG. 1 is a
perspective view showing the basic structure of a printing
apparatus 10 of this embodiment. As shown in FIG. 1, the printing
apparatus 10 includes a base 11, and a carriage 12 is constructed
to freely reciprocate with respect to the base 11.
[0032] The carriage 12 constitutes an ink-jet recording head body
13, and can mount therein a cartridge 13a for black ink and a
cartridge 13b for yellow, cyan and magenta. A recording head 15 is
provided below the carriage 12 so as to be opposed to a recording
sheet 14. A lower end face of the recording head 15 is a nozzle
formation face 15a, and can discharge ink.
[0033] A part of a timing belt 16 is fixed to this carriage 12. An
insertion hole 17 is formed in the carriage 12, and a long guide
shaft 18 can be inserted through this insertion hole 17. Thus, when
a carriage motor 19 is rotated, the timing belt 16 is driven, and
the carriage 12 is moved along the guide shaft 18 by the driving of
this timing belt 16.
[0034] A roller member 20 is rotatably provided on a lower side of
the inside of the base 11. The roller member 20 is provided to be
rotatable by a gear train 21 existing on the other end side of the
base 11. The recording sheet 14 supplied to the printing apparatus
10 is moved in the sub-scanning direction of the recording head 15
by the rotation of the roller member 20. In order to rotation-drive
the roller member 20, a not-shown paper feed motor is provided on
the other end side of the inside of the base 11.
[0035] Here, the roller member 20 is provided only in a region
(printing region) where printing is performed to the maximum in the
inside of the base 11. A non-printing region where the roller
member 20 is not provided in the inside of the base 11 is a home
position where an after-mentioned cap unit 40 is provided.
[0036] On the bottom side of the base 11 in the home position 22, a
tube pump 30 as a suction pump as shown in FIG. 2 and FIG. 3 is
provided. The tube pump 30 includes a pump frame 32 whose plane
shape is an arc, and a flexible tube 31 is disposed along the
inside surface of the pump frame 32. Its one end (right end in the
drawing) is connected to a not-shown connection pipe of a cap head
90, and the other end (lower end of the drawing) is connected to a
not-shown waste liquid tank.
[0037] Roller support grooves 34a and 34b are provided in a pump
wheel 33 of the tube pump 30. Roller support shafts 35a and 35b are
inserted therein, and hold support rollers 36a and 36b rotatably
and movably. Insertion openings 39a and 39b are provided at ends of
the roller support grooves 34a and 34b, and the roller support
shafts 35a 35b are inserted from the portions at the time of
assembly. Engagement grooves 37a and 37b each recessed in a
substantially L shape are formed in part of the pump frame 32, and
guide members 38a and 38b formed of elastic member are fitted
therein. The tube pump 30 as stated above performs a suction
operation when the pump wheel 33 is driven by an after-mentioned
stepping motor 121.
[0038] As shown in FIG. 2, when the pump wheel 33 is driven in the
clockwise direction (direction of an arrow A), since the guide
members 38a and 38b press the rollers 36a and 36b in the
counterclockwise direction, the rollers 36a and 36b moves to the
ends opposite to the insertion openings 39a and 39b of the roller
support grooves 34a and 34b. Here, since the diameters of the
roller support grooves 34a and 34b become large toward the
direction opposite to the insertion openings 39a and 39b, the
rollers 36a and 36b move toward the outside. As a result, since the
rollers 36a and 36b rotate while pressing the flexible tube 31
toward the outside, the liquid and gas in the inside of the
flexible tube 31 are moved in the direction of the arrow A. As a
result, the ink is moved from the cap head 90 to the waste liquid
tank.
[0039] As shown in FIG. 3, when the pump wheel 33 is driven in the
counterclockwise direction (direction of an arrow B), since the
guide members 38a and 38b press the rollers 36a 36b in the
clockwise direction, the rollers 36a and 36b move toward the
insertion openings 39a and 39b of the roller support grooves 34a
and 34b. As a result, the rollers 36a and 36b move toward the
inside, and there occurs a state where the rollers 36a and 36b are
in slight contact with the flexible tube 31. Thus, by keeping this
state, it is possible to prevent the inner walls of the flexible
tube 31 from adhering to each other.
[0040] Next, a control system of the printing apparatus shown in
FIG. 1 will be described. FIG. 4 is a block diagram showing the
control system of the printing apparatus shown in FIG. 1. As shown
in this drawing, the control system of the printing apparatus
includes a CPU (Central Processing Unit) 110, a ROM (Read Only
Memory) 111, a RAM (Random Access Memory) 112, an EEPROM
(Electrically Erasable and Programmable ROM) 113, an I/F
(Interface) 114, an I/O (Input and Output) 115, a bus 116, an
input/output circuit 117, a motor control circuit 120, a stepping
motor 121, a sensor 122, a recording head driver circuit 123, and a
recording head 115. A personal computer (PC) is connected to the
I/F 114.
[0041] Here, the CPU 110 performs various arithmetic processings
according to programs stored in the ROM 111 and the EEPROM 113, and
controls the respective parts of the apparatus including the
stepping motor 121.
[0042] The ROM 111 is a semiconductor memory storing various
programs and various data to be executed by the CPU 110.
[0043] The RAM 112 is a semiconductor memory to temporarily store
programs and data which become execution objects of the CPU
110.
[0044] The EEPROM 113 is a semiconductor memory in which specified
data of results of the arithmetic processing of the CPU 110 are
stored and the data is held even after the power supply of the
printing apparatus is cut off.
[0045] The I/F 114 is a device to suitably transform a
representation format of data when information is given to and
received from the personal computer 130.
[0046] The bus 116 is a signal line group to mutually connect the
CPU 110, the ROM 111, the RAM 112, the EEPROM 113, the I/F 114 and
the I/O 115 and to enable information to be given and received
among them.
[0047] The motor control circuit 120 includes a logic circuit and a
drive circuit as described later, and controls the stepping motor
121 according to the control of the CPU 110.
[0048] The stepping motor 121 is constructed of, for example, a
two-phase stepping motor, and drives the tube pump 30 shown in FIG.
2 and FIG. 3 according to the control of the motor control circuit
120.
[0049] Incidentally, in the example shown in FIG. 4, although only
the stepping motor 121 to drive the tube pump 30 is shown,
actually, a not-shown stepping motor to drive the roller member 20,
and a stepping motor (carriage motor 19) to drive the carriage 12
in the main scanning direction are also controlled by a control
circuit similar to the motor control circuit 120.
[0050] The sensor 122 includes, for example, a recording sheet
sensor, an ink remaining amount sensor, an accumulated working time
sensor and the like, detects various states of the printing
apparatus, and outputs them to the I/O 115 through the input/output
circuit 117.
[0051] The recording head driver circuit 123 is connected to the
recording head 15 and is a driver to perform control for
discharging ink. As described before, the recording head 15
discharges inks of various colors from plural nozzles according to
the control of the recording head driver circuit 123, and prints a
desired image and character on the recording sheet 14.
[0052] FIG. 5 is view showing a detailed structural example of the
motor control circuit 120. As shown in this figure, the motor
control circuit 120 includes, as main components, a logic circuit
120a, a drive circuit 120b, and a thermal shutdown circuit
120c.
[0053] Here, the logic circuit 120a as the control circuit receives
set data from the CPU 110 through the input/output circuit 117,
sets the operation environment, and controls the drive circuit 120b
according to the control data supplied from the CPU 110. The drive
circuit 120b as a switching circuit switches electric power
supplied from a not-shown power source based on the control of the
logic circuit 120a, and drives the stepping motor 121.
[0054] More specifically, the motor control circuit 120 determines
the current amount of chopping current to be outputted to the
A-phase and B-phase based on the control data supplied from the CPU
110. Besides, the motor control circuit 120 sets the decay of the
chopping current based on the control data supplied from the CPU
110. The decay indicates the regenerative method of current at the
chopping off time, and includes a slow decay, a fast decay, and a
mixed decay. The slow decay is a method in which a switching
transistor is held in an on state, and the current is regenerated
through the transistor. The fast decay is a method in which the
transistor is brought into an off state, and the current is
regenerated through a diode for regeneration. The mixed decay is a
method in which these are mixed.
[0055] FIGS. 6A and 6B are views each explaining the details of the
drive circuit 120b. FIG. 6A is a view for explaining the operation
of the slow decay. Here, the drive circuit 120b includes, as main
components, transistors Q1 to Q4, diodes D1 to D4, a coil L, a
resistor R, a power source V1, a reference voltage source V2, and a
comparator C. Here, the transistors Q1 to Q4 switch the current
flowing to the coil L. The diodes D1 to D4 are diodes for a
flywheel (regeneration). The coil L is a coil for excitation
incorporated in the stepping motor 121. The power source V1
supplies power source electric power to the stepping motor 121. The
resistor R is a resistor for detecting the current flowing to the
coil L. The reference voltage source V2 supplies a reference
voltage to the comparator C. The comparator C compares the current
flowing to the coil L with the reference voltage, and outputs a
signal according to its intensity.
[0056] Here, the operation in the case where the electric power is
supplied to the coil L is the same in both the slow decay and the
fast decay. As indicated by alternate long and short dash lines in
FIGS. 6A and 6B, the transistors Q3 and Q2 are simultaneously
brought into on states, and the electric power is supplied to the
coil L through the transistor Q3, the coil L, the transistor Q2,
and the resistor R.
[0057] In the case where the supply of the electric power to the
coil L is stopped, in the slow decay, as shown in FIG. 6A, the
transistor Q3 is brought into an off state, and the transistor Q2
keeps the on state. As a result, the regenerative current from the
coil L flows through the diode D4, the transistor Q2, and the
resistor R as indicated by a broken line.
[0058] On the other hand, in the case of the fast decay, when the
supply of the electric power to the coil L is stopped, as shown in
FIG. 6B, both the transistors Q3 and the transistor Q2 are brought
into off states. As a result, the regenerative current from the
coil L flows to the power source V1 through the diode D4 and the
diode D1 as indicated by a broken line.
[0059] In the case of the slow decay, by the influence of the on
resistor of the transistor Q2 and the resistor R, the decrease of
the regenerative current becomes gentle as compared with the case
of the fast decay. FIG. 7A shows the waveform of the current
flowing to the coil L in the case of the slow decay. FIG. 7B shows
the waveform of the current flowing to the coil L in the case of
the fast decay. From the comparison of these figures, in the fast
decay, the attenuation of the current is steep as compared with the
slow decay. Besides, in the fast decay, as compared with the slow
decay, a current amplitude "a" is large. From these, in the fast
decay, since the current waveform is abruptly attenuated, as
compared with the slow decay, the responsiveness of the control is
high. However, since the current amplitude "a" is large, the
operation sound is large, and the loss is also large. The mixed
decay in which the fast decay and the slow decay are combined has
both of these features.
[0060] The motor control circuit 120 sets, based on the set data
supplied from the CPU 110, an off time in which the transistor of
the drive circuit 120b is in an off state. FIGS. 8A and 8B are
views each explaining the off time. FIGS. 8A and 8B are views for
explaining the operations of the cases where different off times
are set. When the transistor is brought into the on state, the
current flowing to the coil L is increased, and when the current
reaches a current value determined by an instruction value, the
transistor is brought into the off state, and the current is
decreased. When the time set by the off time has passed, the
transistor is again brought into the on state, and the operation
similar to the foregoing case is repeated. The on time is
determined by the inductance value of the coil L and the resistance
value of the closed circuit. Accordingly, in the case where the off
time is set to be short (in the case of FIG. 8B), the switching
frequency becomes high. On the other hand, in the case where the
off time is set to be long (in the case of FIG. 8A), the switching
frequency becomes low.
[0061] Referring back to FIG. 5, the thermal shutdown circuit 120c
as a stop circuit detects the temperature of the motor control
circuit 120, and in the case where the detected temperature
exceeds, for example, 140.degree. C., the operation of the drive
circuit 120b is stopped, and the motor control circuit 120 is
protected. In the circuits constituting the motor control circuit
120, since the heat generation amount of the drive circuit 120b is
largest, the thermal shutdown circuit 120c is disposed in the
vicinity of the drive circuit 120b, and the heat of the portion may
be detected.
[0062] Next, the operation of the above embodiment will be
described.
[0063] In the case where the instruction of a specified process is
issued from the personal computer 130, the CPU 110 controls the
motor control circuit 120 based on the program stored in the ROM
111 as the need arises and drives the stepping motor 121.
[0064] For example, in the case where the instruction to drive the
stepping motor 121 (for example, the instruction of a process to
clean the recording head 15) is issued, the CPU 110 supplies the
set data to the motor control circuit 120 and performs the setting.
Specifically, the set data to select one of the fast decay and the
slow decay shown in FIGS. 6A to 7B is sent, and the value of the
output current flowing to the coil L is set. As the output current,
a selection is made among, for example, 100%, 60% and 20%.
[0065] When the setting of the decay and the current value is
ended, the CPU 110 sets the off time according to the current set
value and the kind of the decay. FIG. 9 is a view showing a table
storing a relation among the current set value, the kind of the
decay and the off time. In this figure, the current set value
indicates a percentage to the maximum value of current which can be
made to flow to the drive circuit 120. The decay is one of the fast
decay and the slow decay. As shown in FIGS. 8A and 8B, the off time
is a time in which the transistor is continuously in the off state
after the current reaches the instruction value. From the table
shown in FIG. 9, for example, in the case where the current set
value is 100%, when the decay is the fast decay, the set value of
the off time is 35 .mu.s. Incidentally, such information is stored
in the ROM 111, and the CPU 110 reads it as the need arises, and
supplies it to the motor control circuit 120.
[0066] The logic circuit 120a stores the current value supplied
from the CPU 110, the kind of the decay, and the information
indicating the time into a not-shown register, and controls the
drive circuit 120b based on these stored values.
[0067] Here, the off time shown in FIG. 9 is determined from the
viewpoint as described below. That is, in the case where the CPU
110 itself runs away by heat, or a program executed by the CPU 110
has, for example, a bug and runs away because of it, the stepping
motor 121 is put in a state where electric power continues to be
supplied. In the case as stated above, the stepping motor 121
generates heat, and is damaged by heat in some cases. Then, in this
embodiment, the off time is adjusted, so that the thermal shutdown
circuit 120c is operated before the stepping motor 121 is damaged
by heat, and the supply of the current to the stepping motor 121 is
interrupted.
[0068] FIG. 10 is a view showing a relation between the off time
and the heat generation amount of the motor control circuit 120 and
between the off time and the heat generation amount of the stepping
motor 121 in the case where the decay is set to be the fast decay
and the current set value is made 60%. FIG. 10A shows the relation
between the off time and the heat generation amount of the motor
control circuit 120, a curve C11 indicates the relation between the
off time and the heat generation amount of the motor control
circuit 120 in the case where duty is 100%, and a curve C12
indicates the relation between the off time and the heat generation
amount of the motor control circuit 120 in the case where the duty
is 80%. FIG. 10B shows the relation between the off time and the
heat generation amount of the stepping motor 121, a curve C13
indicates the relation between the off time and the heat generation
amount of the stepping motor 121 in the case where the duty is
100%, and a curve C14 indicates the relation between the off time
and the heat generation amount of the stepping motor 121 in the
case where the duty is 80%.
[0069] Here, the duty indicates an operating rate of the stepping
motor 121 per a specified time. In the case where the duty is 100%,
the operating rate in the case where the CPU 110 runs away is
supposed. In the case where the duty is 80%, the maximum operating
rate at a normal use time is supposed.
[0070] A stepping motor burnout area where the heat generation
amount becomes Q2 or higher indicates an area where there is a
possibility that the stepping motor 121 is burnt out by heat
generation. A thermal shutdown area where the heat generation
amount becomes Q1 or higher indicates an area where the thermal
shutdown circuit 120c operates.
[0071] As shown in FIG. 10A, in the motor control circuit 120, when
the off time becomes short, the switching frequency of the
transistor becomes high, and therefore, the heat generation amount
increases. When the heat generation amount becomes Q1 or higher,
the thermal shutdown area is caused where the thermal shutdown
circuit 120c operates. As shown in FIG. 10B, in the stepping motor
121, when the off time becomes short, the iron loss (especially
eddy-current loss) is increased, and therefore, the heat generation
amount is increased. When the heat generation amount becomes Q2 or
higher, the stepping motor burnout area is caused where the
stepping motor 121 is burnt out. In this embodiment, in such a
case, a specified value between T11 and T12 is used as the off
time. That is, when the off time is T11 or shorter, in the case
where the duty is 100%, the heat generation amount of the stepping
motor 121 exists in the stepping motor burnout area, and therefore,
it is necessary that the off time is set to be T11 or longer. When
the off time is T12 or longer, in the case where the duty is 100%,
the motor control circuit 120 does not exist in the thermal
shutdown area, and therefore, it is necessary that the off time is
set to be T12 or shorter.
[0072] In the example of FIG. 10, T1 as the center value between
T11 and T12 is used as the off time. When T1 as stated above is
used as the off time, for example, in the case where the program
runs away and the duty becomes 100%, the thermal shutdown circuit
120c operates, and the operation of the stepping motor 121 is
stopped. On the other hand, in the case where the duty is 80% or
lower (at the time of normal operation), since the heat generation
amount does not fall within the thermal shutdown area, the thermal
shutdown circuit 120c does not operate. Besides, as shown in FIG.
10B, in the case where the off time is T1, since the heat
generation amount does not fall within the thermal shutdown area
both in the case where the duty is 100% and in the case where the
duty is 80%, it is possible to prevent the stepping motor 121 from
being burnt out.
[0073] Accordingly, in the case shown in FIG. 10, when the off time
is set to T1, even at the time of runaway, it is possible to
prevent the stepping motor 121 from being burnt out, and the
thermal shutdown circuit 120c operates to stop the supply of the
electric power to the stepping motor 121, and therefore, it is
possible to prevent the stepping motor 121 from being heated.
[0074] FIG. 11 is a view showing a relation between the off time
and the heat generation amount of the motor control circuit and
between the off time and the heat generation amount of the stepping
motor 121 in the case where the decay is set to be the fast decay
and the current set value is made 100%. FIG. 11A shows the relation
between the off time and the heat generation amount of the motor
control circuit 120, a curve C21 indicates the relation between the
off time and the heat generation amount of the motor control
circuit 120 in the case where the duty is 100%, and a curve C22
indicates the relation between the off time and the heat generation
amount of the motor control circuit 120 in the case where the duty
is 80%. FIG. 11B shows the relation between the off time and the
heat generation amount of the stepping motor 121, a curve C23
indicates the relation between the off time and the heat generation
amount of the stepping motor 121 in the case where the duty is
100%, and a curve C24 indicates the relation between the off time
and the heat generation amount of the stepping motor 121 in the
case where the duty is 80%. When a comparison is made with the case
of FIG. 10, although the decay is the fast decay in both the cases,
the current set value is increased from 60% to 100%, and therefore,
as the heat generation amount is increased, the whole graph shifts
to the right of the figure.
[0075] In the example of FIG. 11, T2 as the center value between
T21 and T22 is used as the off time. When T2 as stated above is
used as the off time, similarly to the forgoing case, for example,
in the case where the program runs away and the duty becomes 100%,
the thermal shutdown circuit 120c operates, and the operation of
the stepping motor 121 is stopped. On the other hand, in the case
where the duty is 80%, since the heat generation amount does not
fall within the thermal shutdown area, the thermal shutdown circuit
120c does not operate. As shown in FIG. 11B, in the case where the
off time is T2, since the heat generation amount does not fall
within the stepping motor burnout area both in the case where the
duty is 100% and in the case where the duty is 80%, it is possible
to prevent the stepping motor from being burnt out.
[0076] FIG. 12 is a view showing a relation between the off time
and the heat generation amount of the motor control circuit 120 and
between the off time and the heat generation amount of the stepping
motor 121 in the case where the decay is set to be the slow decay
and the current set value is made 60%. FIG. 12A shows the relation
between the off time and the heat generation amount of the motor
control circuit 120, a curve C31 indicates the relation between the
off time and the heat generation amount of the motor control
circuit 120 in the case where the duty is 100%, and a curve C32
indicates the relation between the off time and the heat generation
amount of the motor control circuit 120 in the case where the duty
is 80%. FIG. 12B shows the relation between the off time and the
heat generation amount of the stepping motor 121, a curve C33
indicates the relation between the off time and the heat generation
amount of the stepping motor 121 in the case where the duty is
100%, and a curve C34 indicates the relation between the off time
and the heat generation amount of the stepping motor 121 in the
case where the duty is 80%. When a comparison is made with the case
of FIG. 10, although both are the same in that the current set
value is 60%, the decay is changed from the fast decay to the slow
decay, and therefore, as the heat generation amount is decreased,
the whole graph shifts to the left of the figure.
[0077] In the example of FIG. 12, T3 as a value between T31 and T32
is used as the off time. When T3 as stated above is used as the off
time, similarly to the foregoing case, for example, in the case
where the program runs away and the duty becomes 100%, the thermal
shutdown circuit operates, and the operation of the stepping motor
121 is stopped. On the other hand, in the case where the duty is
80%, since the heat generation amount does not fall within the
thermal shutdown area, the thermal shutdown circuit 120c does not
operate. As shown in FIG. 12B, in the case where the off time is
T3, since the heat generation amount does not fall within the
stepping motor burnout area both in the case where the duty is 100%
and in the case where the duty is 80%, it is possible to prevent
the stepping motor 121 from being burnt out. Incidentally, T3, T1
and T2 have the relation of T2>T2>T3.
[0078] When the current set value, the decay, and the off time are
set in the manner as stated above, the logic circuit 120a controls
the drive circuit 120b based on the control data supplied from the
CPU 110. The drive circuit 120b controls and rotates the stepping
motor 121 according to the control of the logic circuit 120a. When
the stepping motor 121 is rotated, the tube pump 30 connected to
the motor is driven, and the cleaning process of the recording head
15 is performed.
[0079] During the cleaning process of the recording head 15, for
example, in the case where the program stored in the ROM 111 runs
away and there occurs such a state that electric power continues to
be supplied to the stepping motor 121 from the drive circuit 120b
(in the case where the duty becomes substantially 100%), as shown
in FIGS. 10 to 12, irrespective of the setting of the current value
and the decay, the thermal shutdown circuit 120c operates to stop
the operation of the drive circuit 120b, and therefore, it is
possible to prevent the stepping motor from being excessively
heated. Besides, even in the case where the duty is 100%, since the
stepping motor 121 does not fall within the stepping motor burnout
area, it is possible to prevent the stepping motor 121 from being
damaged by heat.
[0080] In the case where the thermal shutdown circuit 120c is
operated, the CPU 110 supplies restart data to the thermal shutdown
circuit 120c through the logic circuit 120a, so that resetting can
be performed.
[0081] According to the above embodiment, the off time is set
according to the kind of the decay and the current set value, and
in the case of the abnormal operation where the duty is 100%, the
thermal shutdown circuit 120c operates, and in the case of the
normal operation where the duty is 80% or lower, the thermal
shutdown circuit 120c does not operate. Thus, in the case where the
abnormal operation occurs due to the runaway of the program or the
like, the thermal shutdown circuit 120c operates, and the supply of
electric power to the stepping motor 121 is stopped, and therefore,
it is possible to prevent the stepping motor 121 from being heated.
Besides, even in the case where the duty is 100%, the heat
generation amount is made not to fall within the stepping motor
burnout area, and therefore, it is possible to prevent the stepping
motor 121 from being burnt out.
[0082] Incidentally, the above embodiment is an example, and there
are various modified examples in addition to this. For example, in
the above embodiment, although the center value between T11 and
T12, between T21 and T22, or between T31 and T32 is set as the off
time, a value other than the center value can also be set.
[0083] Besides, in the above embodiment, in the case where the duty
is 100%, the off time is selected so that the heat generation
amount does not fall within the stepping motor burnout area.
However, if the thermal shutdown circuit 120c certainly operates
before the stepping motor is burnt out, the heat generation amount
may fall within the stepping motor burnout area. Specifically, for
example, in FIG. 10, the off time may be set in an area not higher
than T11. Besides, since it is conceivable that the stepping motor
burnout area and the thermal shutdown area are changed according to
the environmental change and the individual difference, in order to
cope with such a case, for example, in the example of FIG. 10, the
off time can also be set in an area not lower than T12.
Incidentally, in such a case, although the stepping motor 121
continues the operation state, since the heat generation amount
does not fall within the stepping motor burnout area, the stepping
motor 121 is not burnt out.
[0084] Besides, although the above embodiment has been described
while the stepping motor 121 to drive the tube pump 30 is used as
an example, the invention can also be applied to the stepping motor
used for purposes other than this.
[0085] Besides, although the above embodiment has been described
while the stepping motor 121 is used as an example, the invention
can be applied to, for example, a DC motor.
[0086] Besides, although the above embodiment has been described
while the fast decay and the slow decay are used as examples, the
invention can be applied to, for example, the mixed decay in which
these are combined. FIG. 13 is a view showing a current waveform in
the mixed decay. As shown in this figure, in the mixed decay, when
a current value reaches an instruction value, first, the current is
abruptly decreased by the fast decay, and subsequently, the current
is gradually decreased by the slow decay. In this case, the total
time (.tau.1+.tau.2) of a time .tau.1 of a portion corresponding to
the fast decay and a time .tau.2 of a portion corresponding to the
slow decay is set as the off time. Incidentally, only .tau.1 or
.tau.2 may be set as the off time.
[0087] Besides, in the above embodiment, although the duty at the
time of normal operation is made 80% or lower, it may be set to a
value other than this. For example, the duty can also be made 90%
or lower, or 70% or lower.
[0088] Besides, the above embodiment has been described while
using, as an example, as shown in FIGS. 10 to 12, the case where
the curve indicating the relation between the off time and the heat
generation amount of the motor control circuit 120 is positioned at
the right side of the curve indicating the relation between the off
time and the heat generation amount of the stepping motor 121.
However, in the case where the curve indicating the relation
between the off time and the heat generation amount of the motor
control circuit 120 is positioned at the left side of the curve
indicating the relation between the off time and the heat
generation amount of the stepping motor 121, even in the case where
the heat generation amount is positioned in the stepping motor
burnout area, there is a case where the heat generation amount does
not fall within the thermal shutdown area. In such a case, the
capacity of the stepping motor is made large, or a member (for
example, cooling fin) for cooling is attached to the stepping motor
in order to improve the heat radiation characteristic, and in the
case where the heat generation amount is positioned at least in the
stepping motor burnout area, the heat generation amount is made to
fall within the thermal shutdown area.
[0089] Besides, in the above embodiment, although the two-phase
stepping motor 121 is used, a one-phase or a three- or more phase
stepping motor can also be used.
[0090] Besides, in the embodiment, although the CPU 110 generates
the control signal, and the logic circuit 120a receives this and
drives the drive circuit 120b, the sharing of roles is not limited
to the case as stated above. For example, the logic circuit 120a
can substitutes for the function of the CPU 110.
[0091] Besides, in the embodiment, although the stepping motor
burnout area and the thermal shutdown area are fixed, it is
conceivable that these are changed by the heat radiation
characteristic or environmental temperature. Thus, for example, the
environmental temperature is detected by a sensor, these areas are
redefined according to the detected result, and the off time may be
set according to the redefined areas. According to such an example,
it is possible to provide a stepping motor control apparatus which
hardly receive the influence of the environmental temperature or
the like.
[0092] Incidentally, the above processing function can be realized
by a computer. In that case, there is provided a program describing
the processing content of the function which the stepping motor
drive apparatus should have. The computer executes the program, so
that the above processing function is realized on the computer. The
program describing the processing content can be recorded on a
computer readable recording medium. The computer readable recording
medium includes a magnetic recording device, an optical disk, a
magneto-optical recording medium, a semiconductor memory, etc. The
magnetic recording device includes a hard disk device (HDD), a
flexible disk (FD), a magnetic tape, etc. The optical disk includes
a DVD (Digital Versatile Disk), a DVD-RAM, a CD-ROM (Compact Disk
ROM), a CD-R (Recordable)/RW (ReWritable), etc. The magneto-optical
recording medium includes MO (Magneto-Optical disk), etc.
[0093] In the case where the program is put into circulation, a
portable recording medium, such as, for example, a DVD or a CD-ROM
on which the program is recorded, is sold. Besides, the program is
stored in a storage device of a server computer, and the program
can be transferred from the server computer to another computer
through a network.
[0094] The computer to execute the program stores, for example, the
program recorded on the portable recording medium or the program
transferred from the server computer into its own storage device.
The computer reads the program from its own storage device, and
executes the processing in accordance with the program.
Incidentally, the computer directly reads the program from the
portable recording medium, and can execute the processing in
accordance with the program. Besides, the computer can perform the
processing in accordance with the received program each time the
program is transferred from the server computer.
* * * * *